Re: [PATCH] Add rdma service for kernel boot support

[Benjamin Drung <benjamin.drung-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>]

Hi Jason,

Am Donnerstag, den 13.07.2017, 16:15 -0600 schrieb Jason Gunthorpe:
> On Thu, Jul 13, 2017 at 06:33:07PM +0000, Bart Van Assche wrote:
> > On Thu, 2017-07-13 at 12:20 -0600, Jason Gunthorpe wrote:
> > > Here is an untested attempt to move module loading into
> > > srp_daemon -
> > > what do you think Bart?
> > 
> > Hello Jason,
> > 
> > Thanks for the patch. To me this looks like a nice simplification
> > compared
> > to the current approach. Do you want me to test this patch?
> 
> I did some more steps..
> 
> Benjamin/Bart let me know what you think, I'll send the patches to
> the
> list if you like the idea.
> 
> https://github.com/jgunthorpe/rdma-plumbing/tree/systemd
> 
> This replaces Benjamins rdma.conf based approach.
> 
> The basic approach is to directly use systemd to load the modules and
> determine what modules to load by using udev and explicit Requires in
> the units.

I like your approach very much. It's cleaner and simpler. So let's
ditch my approach and use yours.

I tested your branch on a Debian 8 (jessie) system with a mlx4 card and
found several points to fix/improve/discuss:

1. The rdma-load-modules@ service needs to set DefaultDependencies=no.
Otherwise it will end up in a dependency loop:

Found ordering cycle on rdma-load-modules-A9MMwDI1uB1TDjBF/Jpztg@public.gmane.org/start
Found dependency on basic.target/start
Found dependency on paths.target/start
Found dependency on acpid.path/start
Found dependency on sysinit.target/start
Found dependency on rdma-load-modules-A9MMwDI1uB1TDjBF/Jpztg@public.gmane.org/start
Breaking ordering cycle by deleting job paths.target/start
Found ordering cycle on rdma-load-modules-A9MMwDI1uB1TDjBF/Jpztg@public.gmane.org/start
Found dependency on paths.target/start
Found dependency on acpid.path/start
Found dependency on sysinit.target/start
Found dependency on rdma-load-modules-A9MMwDI1uB1TDjBF/Jpztg@public.gmane.org/start
Starting Load RDMA modules from /etc/rdma/modules/mlx4.conf...

2. You can just specify "etc/rdma/modules" in debian/rdma-core.install
instead of listing each .conf file individually.

3. Default conf files for opa.conf and roce.conf are missing.

4. Should rdma-load-modules@ *not* fail if the corresponding .conf is
missing?

5. How to handle build-in modules correctly? Our kernel has the i40e
module built in (CONFIG_I40E=y) and rdma-load-modules-QqjR1VyAyFhTDjBF/Jpztg@public.gmane.org will
be started, but the system does not have a i40e card and thus I don't
want to have the module started. 

-- 
Benjamin Drung
System Developer
Debian & Ubuntu Developer

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